The invention relates to circuit-breakers and/or motor protection switches. Ordinarily a motor protection switch includes a circuit-breaker having associated therewith a thermal device which protects the motor in a conventional fashion by cutting-out thermal trippers and thus opens the motor circuit. Normally such conventional circuit-breakers include a housing carrying a system of contacts which are controlled by thermal and magnetic trippers. The magnetic system is generally located either on the assembly side of the set of contacts of the housing or on the side opposite thereto, namely, above the set of contacts which are at the bottom of the housing, i.e., the assembly side. A movable armature of the magnetic system is connected by a conventional coupling to a contact-bridge holder of the set of contacts.
In this conventional design the magnetic system together with the surrounding housing is relatively bulky and highly complex making assembly thereof quite difficult. Moreover, the thermal trippers only trip when the current drain, i.e., the thermal load, exceeds a given value, and irrespective of the relatively high complexity of the design of the latter, such thermal trippers are comparatively inert because the current drain or the thermal load increases only slowly, at least most of the time. Therefore, in order to assure that the motor is protected against sudden electrical malfunctions, such as shorts, a further separate circuit-breaking means is required in such conventional circuit-breakers. Heretofore, the latter has been provided by being mounted in a housing separate from the first-mentioned circuit breaker housing, and in order to connect the electrical components of these two housings, a total of eighteen electrical connections must be made.
It is furthermore noted that in order to connect an ordinary circuit-breaker consisting of a set of contacts and a magnetic protection system by means of electrical conductors to a separate motor protection switch, the total number of electrical connections is twelve.
Both of the latter designs entail complex and time-consuming wiring and a substantial expenditure of material is required both for the many conductors and for the many connections between the conductors of the various electrical components of the housing(s). Therefore, there is not only an inordinate expenditure during installation, but such multiple devices are bulky which is particularly disadvantageous when they are installed inside a conventional switch box.